[Experimental study of viremia in immune host in tick-borne encephalitis]

Experimental studies of viremia in immune hosts with tick-borne encephalitis showed that triple vaccination alone, providing antibody accumulation in the blood sera of mice with a neutralization index up to 2.0 led to the survival of not more than 60% of the animals after subcutaneous inoculation of 100 LD50 of virus with the average survival time of 8.5 days. The use of vaccine in combination with exogenous mouse interferon or interferon inducer (RFf2) increased the survival rate to 75% and 80%, respectively, with an increase in the average survival time up to 9 and 9.5 days. The infected animals examined both 1--4 days after infection and at more remote intervals showed no viremia either in the blood serum or in formed elements examined by immunofluorescence. The use of interferon alone or interferon inducer alone without preliminary vaccination increased the survival rate to 55%--60% but did not result in complete elimination of the virus from the blood in the first day after inoculation.